Variable electrical apparatus.



F. LOWENSTEIN.

VARIABLE ELECTRICAL APPARATUS.

APPLICATION FILED AUG. I3. I916.

1,258,423. Patented Mar. 5, 1918.

2 SHEETS-SHEET I.

nveniom F. LOWENSTEIN.

.VARIABLE ELECTRICAL APPARATUS.

APPLICATION HLED AUG. 10, 1916- 1,258,423. Patented Mar. 5, 1918.

2 SHEETS-SHEET 2 F BROOKLYN, raw YORK.

VARIABLE ELECTRICAL APPARATUS.

v lpectflcatton of Letters Patent. I

Patented Mar. 5, 1918.

Original ammuua and m. as, 1010, lerlal Io. man. 7 Divided and um application fled a 10, mo. Serial llo. 114,200.

To all whom it may concern:

Be it known that I, Fm'rz Lowmzs'rzm, a

' citizen of the United States, residin at Brooklyn in the county of Kings and tate of New York, have invented certain new and useful Improvements in Variable Electrical Apparatus; and I do hereby declare the following to be a full, clear, and exact descri tion of the invention, such as will enab e others skilled in the art to which it appertains to make and use the same.

This invention relates to variable electrical apparatus and more particularly to variable condensers adapted or use in wireless or radio work.

As heretofore-constructed, variable condensers have been so designed that equal angular movements or displacements of the movable condenser plates within the working range of the instrument have produced unequal percentage variations in capacity. As set forth in my copending application, Serial No. 569,324, filed June 28, 1910, of wliich the present application is a division, I have found it desirable for certain purposes in the wireless art that equal angular movements of the movable plates should produce equal percentage changes in capacity. It is a principal object of the resent invention to produce a condenser 0 this character.

In order that the same percentage change in capacity C ma be produced by a given displacement of t e movable plates at any point X on the characteristic or operating curve of the instrument, it is necessary that n n1 n+1 Cl! H T whence n la-1 m n V il-1 11+:

The variations in capacity of the condenser must therefore follow the law of geometrical progression. The equation of the characteristic can be deduced from this consideration, and may take the form where a and bare the lower and upper operating limits of the condenser capac ty and d is the maximum displacement 'for which the instrument is designed.

equivalent expression can be derived from the fundamental consideration that ga constant.

where 0 is the angle of displacement in degrees.

From the foregoing it is evident that the active area of the movable surface of a con-- denser constructed in accordance with the invention, neglecting edge effects, is

A=ge

In this equation the constants q and m in-' fiuence the minimum and maximum capacitv values and therefore the operating range (if the condenser. In a practical form of rotary condenser embodying the principles of the invention, an operating curve of the desired character can be attained, for example, by making the superposed fixed condenser plates semicircular and of the same size, as is usual; while the movable plates are cut ofi' at such different angles as to produce the logarithmic characteristic desired. I rifiproved apparatus of this descri tion is 1 ustrated'in the accompanying rawings in which Figure 1 is a vertical section of apparatus comprising the cut-oi! plate condenser asso- Fig, 3 is a transverse-section on the line 3-3 of Fig. 1, viewed from below, the cusing having been removed.

The condenser plates'ma be inclosed in a protective casing 10 provi ed with a cover plate 11 and a base p ate 12, both niade of suitable insulating material andsecured together by means of rods 13. The semicircular stationar condenser plates 14 are supported in para lel relation by rods 15, wlnch de nd from the cover plate and are adjust abl:

cl'amped thereto by nuts 16, 17. The rods 15 pass through holes provided in the stationary condenser plates, which are umformly spaced apart by collars 18. A cross piece 19 connects the lower ends of the rods 15, and by means of clampingl nuts 20 21, the s stem of stationary'con ensenplates ma lie firml clamped in fixed position.

he paral el movable condenser plates 21' are suitably secured to a central vertical shaft 22 which is supported at its lower end on an adjustable pivot 23 and is held at its upper end in a bearing 24 in the cover plate. Spacin" collars 25 are provided to maintain the jates 21, the proper distance apart, and they can be securely clamped in position between nuts 26 and 27. The relative positions of the fixed or stationary plates and the movable plates are such that when the central shaft is turned, the movable plates enter the spaces between the fixed plates in a manner to be more fully hereinafter explained. The shaft is arranged to be turned in this instance by a crank 28 secured to the upper end thereof and provided with a crank pin 29. The condenser may be going to the fixed plates through supportmg rods 15, and a lead 31 going to the movable plates through a binding post 32 and conductive strip 33 which makes electrical contact with the upper shaft. bearing.

Returning now to the movable plates, it will be seen that, with the exception of. a few at the top of the set which are full semicircular, they are cut oil atangles which are progressively greater from the top downward. As a result, the edges of the movable set of plates are arranged in steplike fashion, so that the movable plates enter successively a, between thestationary plates as the shaft is turned. The proportionin of the plates and their arrangement is sac that the capacity of the condenser is variable substantially in accordance with the logarithmic law given above. Furthermore, the change in capacityis much more adual than in a condenser of the types eretofore known.

Although the described condenser may be usefully emplo ed otherwise, it is here shown associate with a variable inductance element, also logarithmic in character, in such manner that both inductance and capacity may bevaried together in a reciprocal relation, or each may be varied independently.

This combination forms no part of the present invention, but is described and claimed in my prior application aforesaid.

The mechanism will be briefly described here, however, for the sake of clearness.

In the arrangement here'illustrated, the

movable part of the condenser is turned [by means of the crank 28, crank in 29, era

disk 34, vertically movable s aft 85, and rubber knob 36. Attached to the shaft is an 11 per clutch disk 37. To alower clutch t isk 38is attached a self-inductance arm 39 carrying brush 39'tand wave length pointer 39', the brush being arranged to make contact successively with the contact. points -10, these'latter being electrically connected by means of studs 41 and suitable leads with the tapping-elf points of a suitable self-inductance coil (not shown)- At 42 are ivotally mounted switches, each provided with a bifurcated projecting portion 43 so disposed that one or the other of the arms 0 said portion always lies in the circular path traversed by actuating stud 44 carried by the self-inductance arm. As the self-inductance arm is moved in counter-clockwise direction, 'the self-inductance increases. the-stud acting successively on the switches 42 to cut in additional sections of the inductance coil. The lower clutch disk 38 is arranged to be turned individually on a post 45 by means of a handle 46. Spring *7 surrounding the verticonnected in circuit by means of a lead 30 ally movable shaft 35 is compressed between the upper end of post 5 and the upper clutch disk 37. thereby tending to maintain the clutch members out of mutual engagement. Handle 46 is here shown as pivoted at 48, whereby it may be turned down to press brush 39" into firm contact with any of the contact points.

Both the condenser and the self-induc-' tance can therefore be varied independently, as for example in tuning a wireless circuit. Once tuning has been accomplished, the rubber knob 36 may be pushed down to engage-clutch 37-38, and turning of the knob will then cause an equal angular dis lacement of the capacity and of the self-in. u'ctance. The capacity scale *9 and wave length scale 50 are both carried by the upper clutch member 37. Stationary pointer 49 indicates the capacity readings, while wave lengths are indicated by the pointer 39", before mentioned. In the present instance, clockwise movement of the knob, when the clutch is engaged, causes the capacity to increase and the self-inductance to decrease. To obviate the necessity of holding the knob 36 depressed during the turning of the coupled elements, a compression spring 51 is provided to keep the clutch members in engagement. This spring is confined between the lower end 52 of stationary post or sleeve 45 and washer 53, which latter rests on the hub 54 of the crank disk 34, the crank disk being secured to the [stren h to overcome t I 47.

vertically slidable shaft 35. The therefore tends to force said shaft own wardly to bring the clutch members into mutual engagement and thereby to mechanically couple the inductance and.ca-' pacity elements. Said spring is of sufficient e opposmg spring 11 the position of the parts here shown, spring 51 is prevented from depressin the upper clutch member by means of etch members 55 which are carried on leaf springs 56 secured to-a sleeve 57 Said leaf springs press the latch members inwardly so that their shoulders 58 may en go the under,side of the washer 53. hen the knob 36 is pushed down, the sloping cam surfaces 59 of the crank disk hub throw the latches 55' outwardly, thereby releasing washer 53 and the spring 51 confined thereby, the clutch being thereafter held in engagement by said spring. t is to be understood that while specific mechanism for operatingethe movable parts of the condenser has been described in connection with one practical embodiment of the invention, any other convenient means for rotating the movable condenser plates may be employed. Moreover, it is to be noted that the broad principles of the invention are applicable not only to condensers, but also to other varia le electrical apparatus such as variable in uctanees.

What I claim is: 1. A condenser comprising a set of stationary parallel plates suitab y spaced apart, and a set of movable parallel plates adapted to enter between the stationary plates, the plates of one of said sets being so formed that a given angular displacement of the movable plates. produces substantially the same percenta change in capacity at any point within t 0 range of the instrument.

2. A condenser comprising a set of stationary arallel plates suitabl spaced apart, an a set of movable 'ara el plates adapted to enter between t e stationary plates the plates of one setfbeing so designs and arranged with -to those of the other, that movement 0 the movable plates produces variation of capacity in accordance with the law of geometric progression.

3. A condenser'comprisin'g a set of stationary parallel plates suitably spaced apart, and'a set ofmovable ara lel plates adapted to enter between t e stationary plates, the plates of the movable set being cut of in such'manner that ual dis lacements of the movable plates give eq' percenta'ie changes, in capacity. H

.4. condenser comprising a plurality of relatively movable plates so dimensioned that the change in capacity roduced by a movement of the movable ates is to the movement that produced said change as C is to m' in theequation wherea, b, and dare constants. 5. An electric condenser comprising sta tionary arallel plates and mova ary plates, the edges of the movable plates being'arranged in stc -like fashion te'secure a more gradual c ange of capacity.

6'. An electric condenser com rising stationary arallel plates and mova ileparallel le parallel plates a apted to'enter between the stationplates 3.- apted to enter between the stationing so dimensioned and arranged that relative movement .of said surfaces produces variations in capacity cordance with, the law.

. =P where 0 represents capacity, p and n are substantially in instrument constants, and e is, the base' of N apierian logarithms.

9. Variable electrical apparatus comprising .a fixed element and a movable element cooperating therewith to give 'a variable electricalyalue', the arran ent of said elements being such that t e variations in electrical value produced by movement of said movable element follow substantially the law of geometric progression.

10.'Varia le electrical ap aratus comprising relatively movable ements cooperating to give a variable electrical value,

the arrangement of said elements bein such that the variations .in electrical value produced by relative movement of said elements follow substantially the" law of geometric progression.

In testimony whereof I hereunto allix my signature. I

FRITZ LOWENSTEIN. Witra=wo s s e- H. M. Manna. 

